do-support may appear for pragmatic reasons. For emphasis The auxiliary generally appears for purposes of emphasis, for instance to establish a contrast or to express a correction: Did Bill eat his breakfast? Yes, he did eat his breakfast (did emphasizes the positive answer, which may be unexpected). Bill doesn't sing, then. No, he does sing (does emphasizes the correction of the previous statement). As before, the main verb following the auxiliary becomes a bare infinitive, which is not inflected (one cannot say *did ate or *does sings in the above examples). As with typical do-support, that usage of do does not occur with other auxiliaries or a copular verb. Then, emphasis can be obtained by adding stress to the auxiliary or copular: Would you take the risk? Yes, I would take the risk. Bill isn't singing, then. No, he is singing. (Some auxiliaries, such as can, change their pronunciation when stressed; see Weak and strong forms in English.) In negative sentences, emphasis can be obtained by adding stress either to the negating word (if used in full) or to the contracted form ending in n't. That applies whether or not do-support is used: I wouldn't (or would not) take the risk. They don't (or do not) appear on the list. Emphatic do can also be used with imperatives, including with the copula be: Do take care! Do be careful! In elliptical sentences The auxiliary do is also used in various types of elliptical sentences, where the main verb is omitted (it can be said to be "understood", usually because it would be the same verb as was used in a preceding sentence or clause). That includes the following types: Tag questions: He plays well, doesn't he? You don't like Sara, do you? Elliptical questions: I like pasta. Do you? I went to the party. Why didn't you? Elliptical statements: They swam, but I didn't. He looks smart, and so do you. You fell asleep, and I did, too. Such uses include cases that do-support would have been used in a complete clause (questions, negatives, inversion) but also cases that (as in the last example) the complete clause would normally have been constructed without do (I fell asleep too). In such instances do may be said to be acting as a pro-verb since it effectively takes the place of a verb or verb phrase: did substitutes for fell asleep. As in